Multiple importance sampling (MIS) has become an indispensable tool in Monte Carlo rendering, widely accepted as a near-optimal solution for combining different sampling techniques. But an MIS combination, using the common balance or power heuristics, often results in an overly defensive estimator, leading to high variance. We show that by generalizing the MIS framework, variance can be substantially reduced. Specifically, we optimize one of the combined sampling techniques so as to decrease the overall variance of the resulting MIS estimator. We apply the approach to the computation of direct illumination due to an HDR environment map and to the computation of global illumination using a path guiding algorithm. The implementation can be as simple as subtracting a constant value from the tabulated sampling density done entirely in a preprocessing step. This produces a consistent noise reduction in all our tests with no negative influence on run time, no artifacts or bias, and no failure cases.

Equal-time (5 s) comparison of basic multiple importance sampling with the balance heuristic (Basic MIS), resampled importance sampling (RIS) and our (normal-independent) method applied to image-based lighting computation. While RIS performs similarly to Basic MIS here, our method achieves 2.75× lower normalized mean square error (NMSE) by redefining the pdf of one of the sampling techniques, while taking into account that MIS is being applied. The pdfs are shown in the bottom row. The pdf optimization presented in this paper is general and can be applied in any MIS estimator.

Oh god... Did you find anyone (professional) actually using this mdl stuff? Why do you find it interesting? It's been around for few years afaik and I never seen anyone using this and I never find their demos anyhow impressive or interesting.

Maybe something akin to this: https://www.chaosgroup.com/vrscans would be cool and interesting. I know that large automotive design companies like to make and use scanned materials etc... I have no idea how these things work though..

Maybe something akin to this: https://www.chaosgroup.com/vrscans would be cool and interesting. I know that large automotive design companies like to make and use scanned materials etc... I have no idea how these things work though..

It works that you download a vrscan material, you select a dedicated material and load the downloaded vrscan and you're ok.
At least you know that the material setup is fine...so you have just to set the lighting.
I don't use it cause I don't need that kind of precision and cause the scanned surface is not so much wide and for some architectural materials is it a problem.

As you said, for automotive it's seems quite a standard now, at least for the professionals I know.

Oh god... Did you find anyone (professional) actually using this mdl stuff? Why do you find it interesting? It's been around for few years afaik and I never seen anyone using this and I never find their demos anyhow impressive or interesting.

Yes, idea is nice... But, it's been out for years unless I'm wrong.
So why haven't everybody adopted it to a point where I could go and download or buy 3D models using only or mostly mdl's? Maybe I'm looking in wrong places...?

Also those examples you took from the pdf look terible, but maybe they're underselling this tech?

I think that it would be cool if someone would make an open source scanning solution and format that woul utilize some "AI" networks to build all the complex data from few photos of material under different lighting or something like that...

An open source format with easy do do your own scans could actually take over the whole thing rather than all those ecosystems... maybe